[TeMPOraL]

Oh, printers, inexhaustible source of fun.

My approach for over a decade now has been, before any "manual duplex" printing, to start by marking the top page in the tray with a little arrow pointing upwards, drawn with pencil or pen, in the bottom right corner of the page. I'd then print one page (and/or print a test page), and check the position of the arrow, to learn how the particular printer behaves.

To date, I've probably seen every possible orientation of the arrow on the output. Some printers do insane things to paper.